Core-Shell Silicon Anode Material With Controlled Composite Spacing
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Solution Overview
Problem
Lithium secondary batteries face challenges with silicon anode active materials due to structural collapse from volumetric expansion and reduced lifespan from exposure to electrolytes, as existing methods either decrease initial efficiency or fail to maintain structural integrity during charging and discharging.
Innovation Solution
An anode active material with a core-shell structure, comprising metal particles and carbon, where the distance between adjacent composites is optimized between 80 nm to 300 nm, with a stronger second shell layer to prevent structural collapse and enhance electrical conductivity, and a method involving pulverization, spray-drying, and complexation steps to prepare the material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as anode active material to increase battery capacity, then battery capacity is improved, but structural collapse occurs due to volumetric expansion during charging and discharging
Solution Approach 1:
The patent applies nested shell structures where multiple shell layers surround the silicon core particles. The first shell layer directly contacts the core, the second shell layer surrounds the first, and optionally a third shell layer surrounds the second, creating a nested protective configuration that accommodates volumetric expansion while maintaining structural stability.
Solution Approach 2:
The patent uses composite material structures combining silicon core particles with multiple shell layers made of different materials (carbon, oxides, nitrides, or carbides of silicon, metal, or aluminum). This composite approach allows the core to provide high capacity while the shells provide structural stability and protection.
2Stability of the object's composition
If coating layer is formed on silicon particles to suppress expansion, then structural stability is improved, but coating layer may be damaged during charging and discharging causing simultaneous exposure of all silicon particles to electrolyte
Solution Approach 1:
The patent uses multiple nested shell layers instead of a single coating layer. When the outer shell layers are damaged during charging and discharging, inner shell layers remain intact and continue to protect the silicon core particles from electrolyte exposure, preventing catastrophic failure and extending battery lifespan.
Solution Approach 2:
The patent prepares multiple protective shell layers in advance around the silicon core particles. These pre-formed shell layers act as cushioning protection that absorbs damage progressively, ensuring that even if outer layers are compromised, the silicon particles remain protected by inner layers throughout the battery's operational life.
3Volume of moving object
If silicon particles are pulverized to nanometer level to suppress expansion, then volumetric expansion is reduced, but degree of oxidation increases decreasing initial efficiency
Solution Approach 1:
The patent uses shell layers to protect nanometer-level silicon core particles from oxidation by the electrolyte. The shell layers act as barriers that prevent direct contact between the highly reactive nanoscale silicon and the electrolyte, maintaining initial efficiency while allowing the use of fine particles to suppress volumetric expansion.
Solution Approach 2:
The patent creates composite structures where nanometer-level silicon core particles are combined with protective shell layers. This composite approach allows the silicon to be pulverized to nanometer size for reduced expansion while the shell material (carbon, oxides, nitrides, or carbides) prevents oxidation and maintains high initial efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The anode active material maintains performance and prevents structural collapse, ensuring a longer lifespan of lithium secondary batteries by optimizing the distance between composites and enhancing electrical conductivity through the core-shell structure.
Implementation Method 1
a structural collapse of an active material may occur due to a volumetric expansion by about 300% to about 400%
Implementation Method 2
an oxidation reaction of the silicon may be caused
Data Source
AI summary
An anode active material for a lithium secondary battery includes a plurality of composites that each includes a core, and a first shell layer surrounding the core, and a second shell layer surrounding the plurality of composites. The composites may each include metal particles and carbon, and a distance between adjacent composites among the composites may be in a range of 80 nanometers (nm) to 300 nm.